Manganese(IV) Oxide Production by Acremonium sp. Strain KR21-2 and Extracellular Mn(II) Oxidase Activity
Manganese(IV) Oxide Production by Acremonium sp. Strain KR21-2 and Extracellular Mn(II) Oxidase Activity
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DOI：
10.1128/aem.00417-06
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发表时间：
2006-10
影响因子：
4.4
通讯作者：
N. Miyata;Y. Tani;K. Maruo;H. Tsuno;M. Sakata;K. Iwahori
中科院分区：
文献类型：
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作者：
N. Miyata;Y. Tani;K. Maruo;H. Tsuno;M. Sakata;K. Iwahori
摘要 能够沉积 Mn(III, IV) 氧化物的子囊菌广泛存在于水生和土壤环境中，但参与 Mn 氧化物沉积的机制仍不清楚。 Mn(II) 氧化子囊菌，Acremium sp.菌株 KR21-2，产生具有丝状纳米结构的锰氧化物相。 X射线吸收近边结构（XANES）光谱表明Mn相主要为Mn(IV)。我们从菌株 KR21-2 的培养物中纯化出同质的具有 Mn(II) 氧化酶活性的漆酶样酶。纯化的酶氧化 Mn(II)，产生悬浮的 Mn 颗粒； XANES 光谱表明 Mn(II) 已转化为 Mn(IV)。 Mn(II)氧化的最佳pH值为7.0，表观半饱和常数为0.20 mM。该酶氧化 ABTS [2,2'-azinobis(3-乙基苯并噻唑啉-6-磺酸)]（最适 pH，5.5；Km，1.2 mM），每个分子含有两个铜原子。此外，N末端氨基酸序列(残基3至25)与顶孢霉多酚氧化酶的相应序列有61％的同一性，与漆斑菌胆红素氧化酶的相应序列有57％的同一性。这些结果提供了真菌多铜氧化酶可以将 Mn(II) 转化为 Mn(IV) 氧化物的第一个证据。本研究强化了多铜氧化酶对微生物介导的锰氧化物沉淀的贡献的概念，并表明顶孢菌属。菌株 KR21-2 是了解不同子囊菌中 Mn 氧化的良好模型。
ABSTRACT Ascomycetes that can deposit Mn(III, IV) oxides are widespread in aquatic and soil environments, yet the mechanism(s) involved in Mn oxide deposition remains unclear. A Mn(II)-oxidizing ascomycete, Acremonium sp. strain KR21-2, produced a Mn oxide phase with filamentous nanostructures. X-ray absorption near-edge structure (XANES) spectroscopy showed that the Mn phase was primarily Mn(IV). We purified to homogeneity a laccase-like enzyme with Mn(II) oxidase activity from cultures of strain KR21-2. The purified enzyme oxidized Mn(II) to yield suspended Mn particles; XANES spectra indicated that Mn(II) had been converted to Mn(IV). The pH optimum for Mn(II) oxidation was 7.0, and the apparent half-saturation constant was 0.20 mM. The enzyme oxidized ABTS [2,2′-azinobis(3-ethylbenzothiazoline-6-sulfonic acid)] (pH optimum, 5.5; Km, 1.2 mM) and contained two copper atoms per molecule. Moreover, the N-terminal amino acid sequence (residues 3 to 25) was 61% identical with the corresponding sequence of an Acremonium polyphenol oxidase and 57% identical with that of a Myrothecium bilirubin oxidase. These results provide the first evidence that a fungal multicopper oxidase can convert Mn(II) to Mn(IV) oxide. The present study reinforces the notion of the contribution of multicopper oxidase to microbially mediated precipitation of Mn oxides and suggests that Acremonium sp. strain KR21-2 is a good model for understanding the oxidation of Mn in diverse ascomycetes.